The invention is based on an internal combustion engine, in particular a Diesel engine, of the generic type defined hereinafter.
In a known engine of this type (German Patent Document 30 11 580 Al), an exhaust gas recirculation line is connected to each exhaust pipe leading away from the cylinder, for the purpose of exhaust gas recirculation, and an exhaust gas throttle valve is disposed in the line in order to vary the free cross section of the exhaust gas recirculation line. Downstream of the exhaust gas throttle valve is the exhaust gas manifold, from which branch lines lead to each intake pipe. One passage control device, which is operated synchronously with the engine rpm, is disposed in each branch line. At the point where the branch line discharges into the intake pipe, a guide tube is inserted into the intake pipe and with it forms an annular conduit.
The branch line discharges into the annular conduit. The guide tube ends immediately upstream of the inlet valve. With this kind of exhaust gas recirculation apparatus, the emissions of nitrogen oxide in the exhaust gas are markedly reduced, and the amount of exhaust gas is well mixed with the fuel and air mixture.
In highly supercharged NKW engines, the use of an exhaust gas recirculation apparatus has previously been avoided, since engine wear increases from soiling, the exhaust gas counterpressure under heavy load is lower than the charge pressure of the charge air compressor, and charge air coolers and compressors become dirty, which markedly reduces their efficiency. Adherence to required exhaust gas limit values in terms of nitrogen oxide emissions is attained here by charge air cooling, high supercharging, and very late injection onset by the fuel injection pump. Because of the late injection onset, however, this adherence is achieved at the cost of an increase of about 10 to 20% in fuel consumption.